1. Field of the Invention
The present invention relates generally to the field of loudspeaker design and specifically to the design of multi-purpose loudspeakers intended to accept single or dual channel audio signal inputs.
2. Background of the Invention
It has become common practice in the design and installation of distributed audio systems to utilize a single loudspeaker to reproduce both channels of a stereo audio system where the location or cost considerations make the use of a stereo pair of loudspeakers undesirable. Such situations may include, by way of example, outdoors where the need to cover a large area with sound makes the use of stereo pairs of loudspeakers both undesirable and impractical, or extension speakers in smaller rooms where more than one speaker would be impractical. It has also become common practice to design such special application loudspeakers in such a way as to accept either a single channel input, for use in stereo pairs, or a dual channel input, for use individually to reproduce both stereo channels. This dual purpose feature increases the applications flexibility of the loudspeaker and reduces the number of different versions of the product that must be manufactured and kept in inventory.
As is well known to those skilled in the art, the single or dual channel capability may be achieved in several different ways. For example, as shown in FIG. 1, such a loudspeaker may include two transducers with two separate inputs and a switch for determining whether the loudspeaker is operating in single or dual channel mode. Another method as shown in FIG. 2, utilizes a single transducer with two separate voice-coil windings, two separate inputs respectively connected to the two voice-coil windings and a switch for determining single or dual channel operational mode. Yet another method, as shown in FIG. 3, combines a dual voice-coil mid-range or low frequency transducer with two separate high frequency transducers. In this case, two separate inputs are connected to separate crossover networks connected respectively to one voice-coil winding and one high frequency transducer, and to the other voice-coil winding and other high frequency transducer. A switch is also employed to determine dual or single channel operating mode. Although not required, the switch is used to determine the operating mode as the switch eliminates the need for additional external wiring when using such a loudspeaker in single channel mode.
Such dual purpose loudspeakers are typically installed as part of a distributed audio entertainment system either by a professional installer or by the end user of the product. Upon installation, the installer is required to choose the correct operating mode and to make the proper connections to the inputs for that operating mode. Typically, nothing prevents the installer from incorrectly setting the operating mode switch or from making the wrong input connections for the chosen operating mode. As is also well known to those skilled in the art, if the input connections do not match the operating mode selected by the switch, the loudspeaker will not perform correctly. Depending on the specific configuration of the loudspeaker circuitry, damage to the amplifier or loudspeaker may also occur as a result of improper installation.
Accordingly, needed in the art is a way to prevent improper connections to the inputs of a single-dual channel loudspeaker. Also needed in the art is a way to indicate that the proper operating mode has been chosen and that the proper connections have been made.